1. The outer layer or membrane of a cell, especially in certain protozoans and microorganisms.
Usage: biology; technical

Examples

• The periplast of the ciliate protozoans serves as a protective barrier.
• Under the microscope, the periplast appeared as a thin, translucent layer surrounding the organism.
• The periplast helps regulate what enters and exits the cell.
• Biologists studied how the periplast responds to environmental changes.